Cyclone Joan

{{storm path|Joan 1975 track.png}}

Cyclone Joan originated from a mass of convection that formed northwest of Darwin on 30 November 1975. Due to its possibility of tropical development, the Australian Bureau of Meteorology began to monitor the system, issuing a tropical cyclone alert on the same day. Tracking southwest, the system gained organization, at which time it received the name Joan on the next day.{{cite web|title=Cyclone Joan|url=http://www.bom.gov.au/cyclone/history/pdf/joan_full.pdf|publisher=Bureau of Meteorology|date=July 1979|accessdate=28 July 2012|author=Department of Science and the Environment|location=Perth}} As Joan progressed to the southwest, it steadily intensified in favorable conditions, strengthening into a Category 1 tropical cyclone on the Australian tropical cyclone intensity scale on the same day.{{cite web|title=Tropical Cyclone 4S (Joan) Best Track|url=http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/best_tracks/1976/1976s-bsh/bsh041976.txt|archive-url=https://web.archive.org/web/20120917054329/http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/best_tracks/1976/1976s-bsh/bsh041976.txt|url-status=dead|archive-date=17 September 2012|publisher=Joint Typhoon Warning Center|accessdate=28 July 2012}}

Joan continued to steadily intensify as it moved to the southwest, attaining Category 3 status on 2 December, classifying Joan as a severe tropical cyclone. On 5 December, the cyclone intensified into a Category 5 cyclone, the highest rating on the Australian tropical cyclone intensity scale with winds of {{convert|200|km/h|mph|abbr=on}}. On the next day, the forward motion of the storm slowed as while it passed to the north of Rowley Shoals, before abruptly turning towards the south, toward the Australian coast.{{cite web|title=Pacific Tropical Cyclone Data Portal|url=http://www.bom.gov.au/cyclone/history/tracks/|publisher=Bureau of Meteorology|accessdate=28 July 2012|author=Pacific Climate Change Science Program}} Joan reached its peak intensity on 7 December, as it was moving south, with maximum wind speeds of 215 km/h (130 mph) and a minimum barometric pressure of 915 hPa (mbar; 27.02 inHg), based on Dvorak satellite intensity estimates.{{cite web|title=Tropical Cyclone Joan 30/11/1975 to 10/12/1975|url=http://www.bom.gov.au/cyclone/history/pdf/joan.pdf|publisher=Bureau of Meteorology|accessdate=28 July 2012}}

Heading towards the south, Joan made landfall near Mundabullangana, Western Australia late on 7 December with winds of {{convert|220|km/h|mph|abbr=on}} and an estimated pressure of 915 hPa (mbar; 27.02 inHg). After making landfall, the cyclone steadily weakened over land as it passed over areas of Western Australia. However, after crossing the Hamersley Range on 8 December, Joan began a phase a rapid weakening, and by the end of the day, its maximum sustained wind was only {{convert|100|km/h|mph|abbr=on}}. The system became merged with a broad low pressure area the next day before dissipating on 10 December. However, the Bureau of Meteorology continued to track the storm until 12 December.

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Prior to making landfall on Western Australia, six tropical cyclone alerts and 63 cyclone warnings were issued by the Bureau of Meteorology on Joan. The most severe type, the second cyclone warning phase, began to be initiated in three hour intervals beginning on 6 December after Joan made an abrupt turn towards the south. A total of 23 warnings were issued in the second cyclone warning phase. All locations along the coast from Kuri Bay to Exmouth were issued a tropical cyclone alert or warning at least once during the duration of Cyclone Joan.

Upon making landfall on 7 December, a {{convert|2.6|m|ft|abbr=on}} storm surge was measured in Port Hedland, although surge was estimated to have peaked at {{convert|3.25|m|ft|abbr=on}}. However, since this occurred during lower tides, inundation of inland areas was not as severe as past tropical cyclones affecting the Port Hedland area.{{cite web|title=Tropical Cyclone Joan|url=http://www.bom.gov.au/cyclone/history/wa/joan.shtml|publisher=Bureau of Meteorology|accessdate=28 July 2012}} An estimated 85% of houses on Port Hedland were destroyed, with all structures near the coast being damaged to some degree. Due to nearly constant wave action, beach sand was piled to a depth of {{convert|2|m|ft|abbr=on}}. An estimated 1,000 houses were destroyed in the town due to Joan.{{cite news|title=Windstorm rips through Aussie city|url=https://news.google.com/newspapers?id=Yy9OAAAAIBAJ&sjid=bu0DAAAAIBAJ&pg=3168,3504660&dq=cyclone+joan&hl=en|accessdate=28 July 2012|newspaper=The Spokesman-Review|date=8 December 1975|agency=Associated Press|location=Port Hedland, Western Australia}} 50 families in Port Hedland were left homeless as a result of the cyclone.{{cite news|title=Cyclone Chews Up City|url=https://news.google.com/newspapers?id=wzYwAAAAIBAJ&sjid=zvgDAAAAIBAJ&pg=1732,2433358&dq=cyclone+joan&hl=en|accessdate=28 July 2012|newspaper=Spokane Daily Chronicle|date=8 December 1975|agency=Associated Press|location=Port Hedland, Western Australia}}

Further inland flooding resulted from heavy rains dropped by a weakening Joan. Rainfall peaked at {{convert|591|mm|in|abbr=on}} near the Marandoo mine. Multiple locations recorded either near 24-hour rainfall records or broke the previous 24-hour rainfall records. Flooded streams resulted in washaways along railway lines. In addition the Yule River was flooded by the heavy rains. The total repair cost of damages caused by floods in the Pilbara region totaled to A$1.5 million (US$1.9 million).{{#tag:ref|All USD converted figures are based on the exchange rate from 7 December 1975|group="nb"}} Food supply to Wittenoom became drastically limited after several roads were washed away.{{cite news|title=Town gets beer diet|url=https://news.google.com/newspapers?id=dcdYAAAAIBAJ&sjid=QJIDAAAAIBAJ&pg=2378,4476523&dq=cyclone+joan&hl=en|accessdate=3 August 2012|newspaper=The Age|date=18 December 1975|location=Perth}} It was estimated that the return periods of the floods caused by Joan were in excess of 50 years.

Total damages from the storm were estimated to be at least A$25 million (US$31 million), although no casualties were reported as a result of Cyclone Joan. Due to the severity of the storm, the name Joan was retired after the season.{{RA V Tropical cyclone operational plan}}

{{Portal|Tropical cyclones}}

• List of cyclones in Western Australia
• List of most intense tropical cyclones
• Cyclone Alessia (2013)
• Cyclone Tracy

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{{Retired Australian cyclones}}

{{Category 5 Australian region tropical cyclones}}

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Joan

Joan

Category:Retired Australian region cyclones

Category:1975 in Australia

Category:1974–75 Australian region cyclone season